Liquid automobile clutch control



Feb. 27, 1940. x R. H. KRESS LIQUIDAUTOMOBILE CLUTCH CONTROL Filed Aug. 6, 1935 4 Sheets-Sheet 1 INVENTQR.

ATTORNEY.

o I 0 6 HHSS m R a (O 4 H 6 5 In, lb 8 0 B IO 5'1 u M M T Feb. 27, 1940.

Filed Aug. 6, 1955 4 Sheets-Sheet 4 E E .r

IN VENTOR.

TTORNEY.

Patented' Feb. 27, 1940,

- LIQUID AUTOMOBHLE CLUTCHCO-hlTROL; Ralph H. Kressflilawrence, assignor to 1 Patent Protection Corporation, Lowell, Mass,

a corporation of Massachusetts, trustee Application ag-ta 6, 1e35, Serial N0;-34;915

12 Claims.

This invention relates to valves for controlling liquid operable clutches for automobiles.

"it is especially applicable'to clutches of the diaphragm or central piston type such as shown g and described in my application for United States v LettersHP-atent on Rim release oil clutch, filed I September 28, 1934, Serial No. 745,878, in which reference is" made thereto.

ltains common subject niatter with that applica- I lobtion. Forjsafe andpractic'al operation, a-con- 1 t rol valve of the type indicated-in saidapplicationand in this application is highly desirable, even necessary, for the satisfactory operation of such :a clutch. I Y

While a control valve of this sensitive type l'illilllbfirllSGd to control a mechanical or pneumatic clutch, it is particularly desirable infithe operation of a liquicl'clutch because liquidxis not compressible and has a tendency to respond too 20,, quickly and harshly to any movement of a control button, The main feature of properly hold a liquid operable clutchf in a partially engaged position when necessary for slow starting or parking or when it ,isnecessary to. move the car slightly.

i l use a sliding plug with lateral inlet ports so ggzlocated that'there is no pressure from the inlet .to make it hard to: open the valve but the plug against the dead end" of therecessandthe' other end against the end or head of a control rocij'which is movable inside the dead end recess. There will be substantially nobackpressure on the plug it the liquid outlet-from the clutch is open, but when it is closed and the inlet open,

' thepressure from the pump compresses the clutch"- springs, the diaphragm, or its equivalent, in one d ection and forces the plug back against-the spring in the: other direction until the inlet ports are closed. The pressure of the trapped liquid is transmitted from the clutch back to the plug andfrom leakage, jarring and other causes, the plug moves theregulating spring toa certain Ila-limited amount. When the-trapped liquid is re- This application con- I the valve is to admit and hold steadyany desired amount of pressure even! to the fraction of a pound per square inch and is of the compres- (ol;i92 s5): U

leased, the regulating spring moves-the" plug out to its normal position with reference to the control rod. v

The advantages of this valve are thatit is self-lubricating and, therefore, will not bind, and the arrangement of spring and piston or plug are such that the pressure, admitted through the ports, willautomatically remain the same while the control button is in the sameposition The balancing oi'the back pressure against the plug Working against the spring will cause the entry ports to; open or. close enough to compensate for Whatever liquid leaks out through the moving parts or through the bearings.

By means of this valve and a suitable liquid pressure operable clutch, an automobile can be controlled, with great accuracy and delicacy under such circumstances asfgetting into a narrow spot to park, pushinganother'car ahead,.or.in fact in all the various complicated situations wl'iichconiront the driver of' an automobile. In combination with a liquid operable clutch, it permits the driver to meet all situations which may occur in driving, to'the bestadvantage;

The valve and ports can also be made large or small, but regardless o f-theirsize, their operation i will be very delicate;

We are aware that there are'other pressure I regulating valves of the diaphragm type such as used on air brakes, but the construction of these valves is such as to require too much effort to operate them, making them unsatisfactory for delicate control of a clutch; especially where the control rod is connected to the accelerator.

While I find it very convenient to use a pneumatic pressure tank to providea smooth and steady pressure, and particularly such a tank with trap valve, and while I also prefer to use what is known as a'gear pump, I can omit the tank with its trap valve and instead of a gear pump, can use a pump of the Root blower type a reciprocating pump, aswith my construction or": valve, the parts will automatically move according to the position of the control rod and allow the desired pressure to build up and then re- 1 tain such pressure in the clutch. r a In my preferred construction, with the rim release oil clutch, the device acts as a one-way or non-return valve or valve which allows the liquid to pass through it and out through'the release valve in. the rim of the clutch, the rim valveand the control valve being suitably connected, but the same principle can be used and applied in a three-Way valve wherein the liquid under pressure goes through certainports and a conregulated and retained at any amount which port to release the clutch. Such a clutch con-' struction is shown in my patent to R. H. Kress, Oil pressure automobile clutch control, No. 1,938,- 914, issued December 12, 1933.

The same principle might also be used with a clutch operated by fluid pressure where there was no discharge either at the rim or through a three-way port.

The general principle of thisvalve'is the use of a casing with a cylindrical bore in which a plug is slidable, such plug having extending in from its head a tubular spring recess in which is positioned a compression spring against which bears a head carried by the end of a controlrod, the plug and casing being so made that when the rod is pushed, through its" head and the spring, it moves the plug into a position where a port or ports in the plug will register with a lateral port or ports in the casing, thus permitting liquid under pressure to flow through the ports, through a back pressure chamber opposite the end of the plug, thence through a tube or passage to the clutch.

As liquid under pressure is admitted to the back pressure chamber, it tends to oppose the compression spring and, if the parts are properly arranged, finally forcesback the plug, closing the entry ports and keeping them closedbut retaining in the back pressure chamber and the connections to and in the clutch, liquid at a pressure which is determined by the strength of the plug spring and the position of the control rod and. its head.

If there are any leaks, this back pressure is reduced so that the spring forces open the inlet ports allowing the'pressure to again build up until these ports are again closed. The pressure against the clutch can, therefore, be perfectly is determined by the position of the parts.

In the drawings, are shown the various positions of the plug, including the position with the inlet ports closed and the control rod retracted, and second, the position with the control rod de pressed and held and the ports open, and the third positionwhere the control rod'is in the same position but the spring has been compressed by the back pressure, and the'inlet ports are closed. I

In the drawings, Fig.1 is a side elevation, partly in section, of part of the engine, clutch and adjoining parts of an automobile with a valve of my preferred type in position and cooperating with a release valve and a clutch of apreferred type for cooperation with my control valve.

Fig. 2 is a vertical section of the valve shown in Fig. 1, the valve being shown as closed and the trap valve for the tank being shown as closed.

Fig. 3 is a view similar to Fig. 2, but with the trap valve for the tank open and the control valve partly open, the parts being in the posi-" tion which they will assume when the control rod is first pushed down to open the valve.

Fig. 4 is a vertical section of part of the valve shown in Figs. 1, 2 and 3;after the back pres- 7 sure has closed the inlet ports, leaving the outrelease valve R.

The pump .1 sucks oil through pipe lll from reservoir pan 90 and as shown, forces it through,

Fig. 7 is a verticalsection of another valve of 2,191,669 thethree-way type with the inlet ports closed,

and

Fig. 8 is a view of the same valve with the inlet ports fully open.

Fig. 9 is an elevation partly insection of" the valve shown in Figs. 7 and 8 with the parts in the adjusted position. Figs. 10, 11 and 12 show positions being exaggerated. Fig. 15 is an enlarged, transversevertical sectional view showing parts of Fig. 1. a I

Fig. 16 is a vertical sectional view of a plu removed from the valve.

Fig. 17 is a detail elevation showing 'avalve of the type shown in Figs. 5 and 6 in a position with reference to the drip pan of an automobile. In the drawingsA represents the frame of an automobile with the usual motor,-9il being the motor oil drip pan and 95 the clutch housing with a drip pan 9!, there; being a return pipe 92 for oil from the clutch casing'to the motor cas- 93 is a .conventional g ear shift and '34 a conventional foot board through which is a push button D, normally pressed outward by a spring E is an engine shaft which carries partof the pivoted to the clutch casing at 59 and having another arm fill which terminates in a-piri' M which extends into a slot 6?. in the head '63, of the push button D.

The end 64 of head 63 is so sloped that it so engages a connecting rod 85, slidable in guides- 66, b6 and normally, pressed outward by a spring 6'1 and connected by a pivotat 63 with the corn" trol rod I for the control valve V, that when control push button D is pushed in, it opens the ports of control valve V, permitting fluid, a

such as oil, under pressure to enter the charm her 5! behind the diaphragm bl). and at the same time closes the release valve'R, the liquid under plate 52 fixed-Jon clutch shaft B and thereby con,- I

pressure in chamber. 5! behindxdiaphragm 56, V' causing the clutch plates, it, it toengage clutch I 55 necting the clutch shaft B-with the engine, shaft, 3

E as described in my application for United,

States Letters Patent, Serial No. 745,878, pend I ing herewith. When the control push button D is released, its spring 96 and the spring 6'! return theparts to their places, closing control valve V and open ;ing release valve R,'.whcreupon the oil or other fluid in chamber '55 is discharged through the pipe 4! into the bore 8b in the casing of valve V, pushing back plug 8i against spring 32 and allowing. the oil or other liquid under pressure to pass through the ports 83 and M or through the passage 85 up into pipe lZ'into the tank T which is of the pneumatic type, containing compressed .air whereby. pressure is stored up for use, if andfwhen pump P may notbe. working...

91,66 I I y which the liquid passes into tube 43 through mp ass own, ath us al oil pr ssu p mp which forces oil to the bearings through pipe 45 but, of course, could be an independent pump,

Control valve V has a bore 6, which is shown as, tubular, and connects with the pipe. 43 which leads to the clutch and in. this bore is slidable a P w ch hasa h n a l r itv e a ports 8; h c w e the p uss e do from the position shown in Fig, 2 by the rod I to the position shown in. Fig." 3, register with the lateral port or ports 84in the plug casing, allow- 7, ing liquid under pressure from pipe M to pass through ports. 83 and '84, andthence through end or clutch port III, with which lateral ports 84 they connect, and through the back pressure chamber 9 into thepipe 43, as shown by the arrow in Fig. 3, to engage the clutch. J

Plug 5, as shown in Fig. 16, has in its upper part a tubular spring recess 41in which the head 2, which engages compression spring 3, is slidable when pushed down by'rod I.

As shown, this head 2 'is locked in place by a ring I2 in such of the button. D is maintained, moving onlyif,

manner that wheni'rod I is pulled up, as by spring 67, the plug 5 is pulled back as shown in Fig. 2.

When pressureis applied, as by'the foot, to

acontrol button D, rod I presses against spring I,

3, causing plug 5 to move from the position shown in Fig. 2 more or less, to the position shown'in Fig. 3, and if thereis-pressure from the pump P, the fluid passes through the ports 83, 84, 8- and lIIand through thepressure' chamber 9 into the clutch. When theclutch is fully or partly engaged as desired, the back pressure of .the fluid in pressure chamber. llxagainst the bottomiaces of the parts which form the end I of theplug 5 works against the spring, 3, and so moves plug 5 that ports 8" are wholly or partly closed as shown Fig. 4. The position'of plug 5 is maintainedat an equilibrium if the position and whensome' of the liquid. leaks out between 7 any of the moving parts.

This movement of the Valve plug 5 may appear exaggerated in Figs. 4, 5and 6, as well as in I Fig. 9, but as its-diametermaybe only 1 inch while the diameter of a diaphragm such as 58 may be 10 inches, the relative movement will be as the square of; 1 inch to the square of 10.inches.-. "In 'otherwords, a diaphragm movement of 3 of an inch would mean 'a-plug movement of 1 inch. Obviously, 'suchta relationship .cannot be accurately illustrated and the various views, particularly 4 and 9 are exaggerated. I j

Such a position is shown in Fig.4, the spring 3 being compressed, but the head 2- and rod I,v remaining in their position, as held by the op-- erator, the plug 5 including its ring I2 having been pushed up, closing ports 8and 84 asshown.

' The strength of spring 3 and the position of rod I determine and regulate the pressure on the clutch.

Preferably I form plug 5. with twofconcentric A valve v. such as shown inFig s. 1, 2, 3 and 4,

is what might be called a one-way or non-return valve, as the liquid always goes through in one direction as shown by the arrows and never returns through; the valve. The port III is to provide freedisplacement and avoid vacuum in the bore 6 and spring recess 4.

seats M1 and 468 to prevent leakswhen the valve is closed. I I

In Figs. 5 -andy6 is shown a three-way slide alv pe ati nt e ame inc b n.

E93, the passage, 99 connecti the valve plug to the clutchand then when released, passes back through part of the valve and out a discharge port l4. v i I 2i is the control rod having a head 22 inside of a ring 2!} and bearing against a control compression spring23 in a recess 24 in the plug 25. This plug 25 is slidable in a bore 26 and has a lateral port or ports 28 and an end or clutch port 29 which connects the lateral ports 28 with the end 27 when 28 registers with a lateral port it? in the valve casing, allowing liquid to pass in through an inlet I I, which connectsin any suitable way with a pressure tank or a pump or both, and thence out through the back pressure chamber I29, outlet I3 and tube 43 to the clutch.

to allow liquid to how into the clutch pressure chamber, plug 25 closes the discharge port I4, and when pressure on control rod 2| is removed, plug. 25 is pulled back or is pressedback by back pressure and moves the ports 28 and I8 out from registration, allowing the liquid to flow back through the discharge port 14 and pipe 3M into any suitable place, such as the motordrippan 95, as shown in Fig. 17 and described in said Kress Patent No. 1,938,914. r I

I5 represents a connecting by-pass to allow plug 25' to move freely in the bore 26 without being restrained by dead oil; vacuum or pneumatic pressure. I

No pressuretank nor connection therewith] is shown in Figs. 5 and 6, but this valve might be and the discharge port is closed, and in the dot,-

ted lines Fig. 6, inletand discharge ports are closed but the clutch port is open, the parts be-' ing in the normal running position.

In Figs. 7, 8 and 9 is shown another design of a three-way slide valve G in which I96 is the fluid inlet and 9,7 the fluid outlet, while 98 is a spring pressure trap valve which is lifted by the pressure of the fluid coming in through inlet tank of any suitable design.

ng with a pressure 88 is a port which registers with the lateral port or ports 38in valve plug 35'which is slide able in the bore 35, and is controlled by a spring 33 in recess 3 3 andthe head 32 of a control rod 3i, kept in place by a ring 30. I39 is an end or I clutch port which connects'with lateral ports 38".

'is. the bottom end of the plug 35against which the back pressure in chamber I91 presses while 39 represents discharge ports which, when the plug is in a certain position, register with the. casing discharge port such as 83 shown in Fig. 9.

When in the position shown in Fig. 8, the liquid passes through the passages I96, 88, 38, I39 and 97 to the clutch, but when'the pressure on the rod Si is released and it is returned to the drip pan. This whole-valvej'G may conveniently belocated in the drip pan or a suitable conductor may pass from discharge port 89 into a drip pan.

Fig. 9 shows the ports 38 and 39 of; valve plug 35 in a position which'they assume while liquid Therod 39! has a head 3B2, slidable in recess 3B4 against spring 3%, in plug 355, and is held in place by a ring 3i2. Plug 3% is slidable in bore 396 and has lateral inlet ports 388, which con meet with a clutch or end port 310, through end 3M, and lateral inlet ports 3518 are adapted to register with lateral casing ports 3% which connec-t with pressure inlet 383. 399 is the back pressure chamber and 3H and 3I3 are concentric seats to prevent leaks.

1 In Figall is shown a simplifiedtype of valve K in which 51E! is a valve casing with an inlet port 5'i'8 and with a bore 516 in which is slidable a plug 575 which has no spring recess but merely a top 51% and an end orclutch port ll'll which connects with a plurality of lateral plug ports M8, adapted to register with casing inlet port 518.

Control rod 5 has a head 5'12 between which head and the plug top 57 is a compression spring 5'53. 57! represents the end of the plug and 5'69 the back pressure chamber which coincides with and is part of the connection 413 to the clutch.

In this-construction, the plug 575 on the outside is a straight cylinder instead of having the two annular seats such as it! and M38 in Fig. 2. The ports M8 are circular, there being no spring recess and no ring such as at l2, the back preson the rod 5 1! while a very light compression sure from the clutch being depended upon to close the ports 518 and 678 when pressure is held return spring 569 returns plug 515, spring 5'l3 and head 512 to the normal closed position.

In Fig. 12 is shown at L, another modification in which the plug M is in two separate parts.

210 is the casing in which is a plug bore 216 for a plug M which comprises two parts, namely, the top part 215 in which is a recess 274 for a spring 213 against which'bears a head 212 of control rod 21 l, and the lower part 702 which, as shown, is of cylindrical form and is upwardly pressed by a light returning spring 203 in a recess 103,

which together with holes 202 the space M9 which is part of the lower part 490i bore 215 'constitutes a back pressure chamber.

This part m2 of the plug has a stem H34 upon which the upper part 215 of the plug M normally rests, and has holes 202 to equalize the back pressure through the clutch port 2'57 in the back pressure chamber, these two together forming what amounts to an end port forthe whole plug 275 and 702 from which the backpressure always tends to lift the part 275 of the plug, while the spring 2313 tends to hold the part 702 and stem it up against 215.

In this case, the top rim Bil!) of the part of the plug 102 and the corresponding part Bill of the casing serve the purpose of lateral inlet ports for the fluid pressure coming in through the inlet $82. When the control rod 2' with its head 2'52 and spring 273 are depressed, they carry down i the whole plug M including the part 215, stem H34 and the part Hi2 as a unit, opening the inlet port between 600 and Gill and admitting liquid 9 pressure to. the clutch through the port 211.

When the rod 2ll comesto rest and after a predetermined amount of liquid under pressure has gone into the clutch, the back pressure" through chamber ii? pushes back the part 2'15, allowing spring 283 also to lift the part'lilZ,

thus closing the inlet port @500, Gill so that while of different design, this construction of valve works in the same way as the others.

In Figs. 13 and 14; the valve shows a further modification of this last construction.

In Figs. 13'and 14, M isthe passage from the pump or other device for producing liquid pressure and M5 is the trap valve tohold the pres-' sure in a tan-k connected by the passage 141.

i0 is the casing in which: is a cylindrical bore 16 in which is slidable the part of a compound plug S, which plug has a tubular spring which bears the head 12 of a control rod H. This head is slidablein the top part l'lfi of bore '16, the bore of which is reduced to the size of spring recess ll'l. e

' recess ill for a compression. spring 13 against I4? is a back pressure chamber which, as"

shown, includes the tubular part M4 in which is slidable the valve closure l22 shown as having a spring bore i 23 for the return spring H24 which tends to push it upward against-.21. seat M at the 7 middle of pressure chamber Hi,- This pressure chamber i l'i, through a passage ll, connects with i a liquid pressure clutch of any of the types described. Stem 966i is fixed to closure I22;

I25 represents holes through theclosure i 22 whereby the back pressure of the liquid can get down into the bottoml lil of the back pressure chamber Ml, and SM is the stem of another 010 sure Hi5 whichis seated ina seat IE8 at the bottom end of spring recess ill in the upper part 15 of the plug S. I I

The plug S may be considered as including the parts 15, I22, 9M and I05, and when rod ii-is pushed down, its head 12 forces down the spring 13 and all the above parts ofplug'S, thereby pushing closure i22 from its seat Hi. the lateral inlet port, as shown by the dotted lines in Fig-13, which is seat M, from the 'source This opens of pressure to the clutch. Rod H and spring 13 hold the inlet port open until the back pressure in the back pressure chamber M1, acting against closure I05 and the bottom end of the plug, compresses the spring l3 and closes the inlet" port,

as shown in full lines in Fig. l3. The position of parts l5 in plug S in Fig. 14 is exaggerated.

As thus described, this canand will act as a one-way non-return valve, but if it is desired to use it as a three-way valve, it may be provided I with a discharge port I26 which can be used by so adjusting the control rod II that when released, instead of remaining in the position shown in Fig; 13, it will take the position shown in Fig.- 14, the result of which is that theback pressure lifts the part 15 of the plug from the closure H15 allowing the liquid to be discharged throughseat Hi6 upthrough spring 13 charge port I26.

The purpose of this combination liquid clutch and valve is to allow an automobileoperator to and out through disdepress a control button more or less, to hold it until the regulating spring in that position balances the liquid pressure admitted through the inlet ports which are then closed by the back pressure, and to have all the parts return to' the normal closed position when the foot is removed from the button. There should be no appreciable fluid back pressure when the inlet ports are being opened, but there-should be eitliefa headonthe' end of the control rod togethehwith a r'i'ngin th'e head of the plug to k the plug. as described on page 9, p'ara- 9 ,"or s'ome's'ort of light returning spring n in Flgrll, or 203 in Fig.-' 12, or "I24 in Figs. 13

and 14.

Any of such means or other means may be u's'edfito' normally keep the inlet ports: closed.

With s'ome types or; clutchesv and with a three.- way valve, the elasticity of the clutch diaphragm or of its returning spring, might push back the plug to open the discharge ports when'the foot wasremoved from the control 'rod. In such oases, tlre'diaphragm parts would be the means to normally 'keep'the inlet ports closed, but it is better to ,have some sort -.of light returning spring-f I claim: l. The combination in ,an' automobile; of a liquid operable clutch including a liquid pressure chamber'and a movable clutch member operable by liquidpre'ssure insaid chamber to force the clutch members together-against elastic mechanical nieansiorming partof the clutch, said chamber being connected by conductors with'a source of liquid pressure anda' pressure storage tank, said chamberhaving a discharge port controlled by'a discharge'valve; with a'control valve interin said conductors, said control valve including a' casing in' which is-a cylindrical borehavinr a lateralcasing inlet port from the source or pressureandan axial pressurechamber leadingto' tliic' clutch liquid pressure chamber, a plug slidable in the cylindrical bore having a reguiating spring recess'in its head and an axialout let port in its foot leadingtto the axial pressure chamber, and a'lateral inlet port through theside of the plug leading t'othe outlet port in position and size to register Withfthe lateral casing inlet port; a regulating compression spring positioned in the spring recess a Control rod which engages the regulating spring; and control means to open and close the discharge valve and the control valve, including means tonormally keepthe discharge'valve open and the'control valve closed.

2. The combination in an automobile; of a liquid operable clutch including 'a liquid pressure chamber" and a movable clutch member operable by liquid pressure in said chamber to force the clutch members together against elastic mechanical means forming partcof the clutch, said chamber being connected by conductors with a source of liquid pressure; and having a discharge port controlled by a discharge valve; with a control valve: interposed in saidconductors, said control valve-including a casing in which is a bore having a lateral casing inlet port from the source of pressure'andan',axialpressure chamber at one.

end of the bore leading to the clutch liquid pressure chamber, a plugslidablein the bore having a head and a lateralinlet port through the side of the-plug leading to the axial pressure chamber and in position and size-to register with the .lateral casing inlet port; a regulating compression spring whichengages thejplug head; a control rod which engages the regulating spring; and control means to open and close the discharge valve and the control valve including means to control valve closed.

normally keep thedischarge valve open and the The combination in an automobile; of a liquid. operable clutch includinga liquid pressure chamber and a movable clutch'member operable by liquid pressure in said chamber to force the clutch members together against elastic mechanical means forming part of the clutch, said chamber being connected by conductors with a I source of liquid pressure; with a control valve interposed in said conductors, said control valve including a casing in which is a bore having a lateral casing inlet port from the source of pressure, and an axial pressure chamber at one end leading to the clutch liquid pressure chamber, a

plug slidable in the borehavin'ga head and a lateral inlet port through the side of the plug leading to the axial pressure chamber and in position and size to register with the'lateral casing inlet port; a regulating compression spring which I engages the plug head; a control rod which engages the regulating spring; and control means to open and close. the control valve including means outside the valve to normally keep it closed. Y

i; The combination; of a liquid operable clutch including a liquid pressure chamber and a movable clutch member operable by liquid pressure chamber; a plug slidable in the bore having a head and a lateral inlet port through the side leading to the axial pressure chamber and in position and size to register with the lateral casing inlet port;

engages the regulating spring;"and control means a regulating compression 7 spring which engages the plug head; a control rod which to open and close the control valve including means outside the valve to normally keep it closed. 5. The combination; of a liquid operable clutch including a liquid pressure chamber and. a movable clutch member operable by liquid pressure in said chamber to force the clutch members to- I gether against elastic. mechanical means forming part of the clutch, said chamber being connected by conductors with a source of liquid pressure;

Withacontrol valve interposed in said'co'nductors,

-said'co'ntrol valve-including a casing in which is a bore having a lateral casing inlet port from the source of pressure and a discharge port, an axial pressure chamber at one endleading to the clutch liquidpressure chamber, a plug slidable in the bore and having a head, a clutch port in its foot leading to the axial pressure chamber, lateral inlet 'and'discharge ports through the side of the plug,both-arranged to connect with the axial pressurechamber and respectively in'positionto engage the lateral casing inlet and discharge ports; a regulating compression spring which registers with'the plug head; a control rod which engages the regulating spring; and control means to open and close the control valve including means outside the valve to normally keep it closed. f

6. The combination; of a liquid operable clutch including a liquid pressure chamber and a m'ovable clutch member operable by liquid pressure in said chamber to force the clutch members together against elastic mechanical means forming part of the clutch, said chamber being connected by conductors with a source of liquid pressure; with a control valve interposed in said conductors, said control valve being of the slide plug type and having inlets connecting withthe source of pressure, the inlet ports being of such character that of the valve to close the inlet ports; and controldevices including a rod which engages said spring and means outside the valve to normally keep the inlet ports closed.

'7. The combination in an automobile; of a liquid operable clutch including a liquid pressure chamber and a movable clutch member operable by liquid pressure-in said chamber to force the clutch members together'against elastic mechanv ical means forming part of the clutch to produce back pressure, said chamber being connected by conductors with a source of liquidpressure; with a control valve interposed in said conductors, said control valve being of the slide plug type and having inlet ports connecting with the source of pressure, the inlet ports being of such character that no liquid pressure must be overcome in opening them, and having a pressure chamber connected through the conductors with the clutch liquid pressure chamber and in such position that back pressure therefrom will tend to move the plug against a compression spring forming part of the valve to close the inlet ports; and control devices including a rod which engages said spring.

8. The combination in an automobile; of a liquid operable clutch including a liquid pressure with the clutch liquid pressure chamber and through a plug side port connectingv with the casing side port and the source of liquid pressure; a regulating compression spring which engages the other end of the plug; a control rod which so engages the regulating spring and the plug as to compress the spring and to so move the plug as to allow liquid under pressure to pass through the side ports and end port into the clutch and to pull back the plug and to close the side ports when moved in the other direction; and control means to move the control rod and plug including means outside the valve to normally keep the side ports closed,

'9. A valve for controlling oil pressure comprising a casing in which is a bore in which is slidable a plug having an end discharge port-connecting with a side inlet port, a port leading through the side of said casing bore and communicating at one end with an oil pressure pump and at the other end with the side port in the plug, one end of the bore communicating with the end port in the plug and with an oil pressure operable clutch which includes mechanical elastic means to cretend to so pull the plug and spring as to keep the.

side ports normally closed; I 1

10. A control valve including'a casing in which is a bore from which is a lateral casing inlet port which leads to a source of liquid pressure and an axial pressure chamber at one end which connects with the liquid pressure chamber of a liquid operable clutch or like device which includes elastic mechanical means to produce'back pressure in said chamber, a plug slidable in. the bore, said plug having a closed head and a lateral liquid inlet port through the side of the plug, which inlet port leads to the axial pressure chamber and is in a position and of a size'to register with the lateral casing inlet port, a regulating compression spring which engages the plug head, a

i control rod which engages the regulating spring;

and means outside the valve to operate the controlrod including means to normally keep the liquid inlet port, of the casing and the casing inlet port out of engagement.

, 11. A control valve including a casing in which is a bore from which is a lateral casinginlet port which leads to, a source of liquid pressure and an axial pressure chamber at one end which connects with the liquid pressurechamber of a liquid operable clutch or like device which includes elastic mechanical means to produce back pressure in said chamber, a-plug slidable in the bore, said plug having a closed head and a lateral liquidinlet portthrough the'side of the plug, which inlet port leads to the axial pressure chamber and is in a position and of a size to register with the lateral casing inlet port, a regulating compression spring which, engages the plug head and a control rod which engages the regulating spring. I n c l 12. In a liquid pressure control device, the combination of a liquid operable, clutch which includes an elastic diaphragm of relativelylarge diameter and other, elastic mechanical means to produce back pressure in a pressure tube; with a control valve including a casing in which is a bore from which is a lateral casing inlet port which leads to a source of liquid pressure and-an axial pressure chamber one end of which connects with the pressure tube, there being a plug slid able in the casing bore, said plug having a closed head and a lateral liquid inlet port through one side, which inlet port leads to the axial pressure chamber and is in a position and of a size to reg ister with the lateral casing inlet port; a regu-' lating compression spring between the plug head 

